The human eye is an optical system that forms a sharp image of objects on the retina with the aid of a number of refractive interfaces. In doing so, the light waves pass through the cornea, the aqueous humor in the anterior chamber (camera anterior bulbi), the crystalline lens (lens crystallina) and the vitreous body in the posterior chamber (camera vitrea bulbi), which all have different refractive indices. If the distance from the viewed object changes, it is necessary for the imaging behavior of the optical system to change in order to ensure that an image with the same sharpness is formed on the retina. The human eye does this by altering the shape of the lens with the aid of the ciliary muscle (musculus ciliaris), as a result of which the shape and the position of the anterior and posterior surfaces of the lens change substantially, this being referred to as accommodation. In an intact accommodation system in a young person, the vertex power of the system can in this way change between the remote setting (unaccommodated state) and the near setting (accommodated state) by 14 diopters (accommodation range). Therefore, in a young person with normal sight (emmetropic), objects located between the far point, which is at infinity, and the near point, which is about 7 cm in front of the cornea, can be imaged sharply on the retina.
Since the accommodation capacity of the human eye decreases with age, a number of implantable artificial lens systems with variable focal length have been developed.
Potentially accommodative intraocular lenses are lenses or lens systems which are inserted in place of the natural lens, after the latter has been surgically removed, and which are mainly secured in the capsular bag. By means of a still existing but weak residual contraction of the ciliary muscle, a haptic is intended to permit an axial movement of the lens.
Devices for restoring accommodation capacity have, for example, been described in DE 101 55 345 C2, U.S. Pat. No. 6,638,304 B2, WO 03/017873 A1, U.S. Pat. No. 4,373,218, DE 94 22 429 U1, DE 201 11 320 U1, DE 100 62 218 A1, DE 10139027, WO 02/083033, DE 10125829 A1, US 2004/0181279 A1, US 2002/0149743 and U.S. Pat. No. 6,096,078.
Numerous scientific publications relating to the topic of accommodation capacity of lens systems also exist. Reference is made by way of example to the following publications:
Schneider, H.; Stachs, O.; Guthoff, R.: Evidenzbasierte Betrachtungen zu akkommodativen Kunstlinsen [Evidence-based observations on accommodative artificial lenses], 102nd Annual Convention of the German Ophthalmological Society (Berlin, Germany, Sep. 23-26, 2004) (2004); Kammann, J.; Dornbach, G.: Empirical results regarding accommodative lenses, Current Aspects of Human Accommodation, publishers: Guthoff, R.; Ludwig, K. Kaden Verlag Heidelberg (2001), pages 163-170; Fine, H.; Packer M.; Hoffmann R.: Technology generates IOL with amplitude of accommodation (Ophthalmology Times Special Report, March 15, 2005) (2005); Lavin, M.: Multifocal intraocular lenses—part 1, Optometry Today May 2001 (2001), pages 34-37; Lavin, M.: Multifocal intraocular lenses—part 2; Optometry Today August 2001 (2001), pages 43-44; Nishi, O.; Nishi, K.; Mano, C.; Ichihara, M.; Honda, T.: Controlling the capsular shape in lens refilling, Archives of Ophthalmology 115(4) (1997), pages 507-510; and Fine, I. H.: The SmartLens—a fabulous new IOL technology, Eye World 7(10) (2002).
Systems have already been proposed which use the axial prestressing of the capsular bag to convert an axial movement into a change in refractive power using contraction of the ciliary muscle. For example, it is proposed to use the pressure of the rearwardly deflected capsular bag in order to press a gel partly through an apertured diaphragm and thus influence the radius of curvature of the gel swelling out on the other sides. In this system, however, it has not yet been possible to demonstrate the lasting stability of a gel present in the aqueous humor, nor the satisfactory optical properties of the gel pressed through a diaphragm.
DE 199044441 C1 describes fitting magnets on the capsular bag and on the eyeball to deflect the capsular bag forward and, with contraction of the ciliary muscle, still further forward. The IOL (intraocular lens) fixed in the capsular bag is moved along with this and thus causes a change in the vertex power. With this system being placed in the aqueous humor, the axial travel is limited to as far as the iris and is not sufficient to generate the necessary vertex power in an emmetropic eye with the ciliary muscle relaxed.
German patent application DE 10 2007 008 375.2 describes an active mechatronic system which determines the accommodation requirement and, with the aid of electronics, adjusts an optical system of variable focal length. Such a system with a measuring unit and control electronics must additionally have an energy supply system. The energy supply unit must be able to cover the routine consumption of measuring device, control electronics and optical system. A miniaturized energy supply system sufficient for these purposes and able to cover the power requirement of the electronics is, however, not yet available.
DE 10 2005 038 542 A1 describes a device for restoring accommodation capacity, comprising:                at least one optical system,        at least one data acquisition system for recording the endogenous control signals for pupil diameter or eye movement or accommodation or a combination of the controlled control signals,        at least one data processing system for generating a regulating signal for the optical system from the recorded endogenous control signals,        at least one energy supply system, and        at least one securing system.        
Therefore, this device requires a data acquisition system and an energy supply system.
U.S. Pat. No. 6,120,538 describes, similar to DE 10 2005 038 542 A1, a system with means for processing measured data (range-finder 18 and controller 16) and with a separate energy source (20).
Ophthalmology is still faced with the problem that, from the age of about 45 years, the ability of the human eye to accommodate (adjust the refractive power of the actual lens) sufficiently to a reading distance of about 30 cm decreases. In principle, the artificial lens implanted in a cataract extraction is still unable to focus to different distances. For biological reasons, previous attempts at using intraocular structures, in particular the ciliary muscle activity within the capsular bag, to mechanically change the refractive power of implantable systems have been unsuccessful, nor is this expected to be achieved in the near future.